This study will examine the effect of anti-Human factor D monoclonal antibody (Mab 166-32) on complement activation and inflammation during extracorporeal circulation. A simulated pediatric extracorporeal circuit will be used to create a closed-circuit heart-lung machine. One unit of whole blood from human volunteers is added to the circuit and multiple markers of inflammation then assayed at predetermined intervals during the pump-run. Prior to the pump-run, Mab will be added to the blood. In control subjects an inert Mab will be similarly added. Eight subjects will be studied, 4 controls and 4 studies. The results will be used to determine the activity, therapeutic concentration and effectiveness of Mab 166-32.